1. Field of the Invention
The present invention relates to power converters, and more particularly, to DC to DC converters.
2. Background Art
Turbine generator systems often include a gas powered turbine to provide motive force to an alternator which provides single phase or polyphase AC power to a load. When starting the turbine from a rest position, the alternator can be driven as a motor to provide motive force to the turbine until it is running at a self-sustaining, operational speed. When starting the turbine utilizing the alternator as a motor, it is often necessary to convert DC voltage generated by one or more batteries into an AC voltage of sufficient potential for use by the alternator when driven as a motor. Typically, a power inverter system electrically connected between the batteries and the alternator is utilized to increase the potential of the DC voltage and to convert the increased potential DC voltage into an AC voltage for use by the alternator. More specifically, the power inverter system includes a DC to DC converter to increase the DC voltage of the batteries and a DC to AC power inverter to convert the increased DC voltage into an AC voltage usable by the alternator.
A problem with prior art power inverter systems is that the ground potential of the batteries can float such that when the turbine generator is operating, a large potential difference can exist between the batteries and electrical components of the power inverter system. This large potential difference requires that instrumentation connected between the chassis and the electrical components of the power inverter system be isolated from ground potentials that can achieve 1000 volts DC or more.
It is therefore an object of the present invention to provide a power inverter system which avoids large potential differences between the chassis of the turbine generator and the electrical component of the power inverter system. It is an object of the present invention to provide a power inverter system which can charge the batteries after the turbine generator is running at operating speed. It is an object of the present invention to provide a power inverter system having a DC to DC converter which boosts and controls both the positive and negative DC bus voltages and which provides a common electrical voltage reference which can be adjusted to a potential between, preferably intermediate, the positive and negative voltages of the DC bus. It is an object of the present invention to provide a power inverter system that can generate a low impedance electrical voltage reference (hereinafter "neutral") that can be utilized as a current return path for the electrical components of the power inverter system. It is an object of the present invention to utilize this low impedance electrical neutral as a ground reference for a three-phase output voltage generated by the power inverter system. It is an object of the present invention to provide this neutral without additional electronic components and associated control circuitry. Still other objects of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.